This invention relates to graphic processing systems for delivery of character outputs to be displayed or printed and more particularly to a graphic processing system for storage and delivery of characters in the form of pixel unit information and is suitable for high speed processing when developing characters at given positions.
When displaying characters and graphics or figures on a cathode-ray tube (CRT) in the raster scanning manner, a bit map system has been available which employs a memory (bit map memory) adapted to store information corresponding to each pixel of a display unit. This system adopting the bit map memory has also been used to control output signals to a printer. Conventionally, a procedure to issue character and graphic data to the bit map memory has mainly relied upon software which handles a great amount of data, raising a problem of low processing speed. Especially, in a field of high speed generation of graphic figures, hardware is dedicated thereto in some applications but is problematically expensive.
On the other hand, a trend of incorporating the function of generating character and graphic data into an LSI has been proposed as reported in publications such as,
(1) xe2x80x9cGraphic Display Processor to Integrate Drawing Algorithms and Display Controlsxe2x80x9d by K. Katsura, H. Maejima et al, Proceeding of Wescon ""84, No. 2313, November, 1984, and
(2) xe2x80x9cAdvanced CRT Controller for Graphic Displayxe2x80x9d by K. Katsura, H. Maejima et al, Hitachi Review, Vol. 33, No. 5, pp 247-255, October, 1984.
This LSI permits remarkable speed-up of graphic processing at relatively low costs. In addition, the LSI also has a function of copying and transferring information in a rectangular region at high speeds, which function may be applied to character display. Details of the copying function are proposed by the present inventors in U.S. patent application Ser. Nos. 686,039 filed Dec. 24, 1984 and Ser. No. 727,850 filed Apr. 26, 1985 which issued as U.S. Pat. Nos. 4,862,150 and 4,779,210, respectively. The system applying the copying function to the bit map character display can afford to greatly promote the processing speed as compared to the prior art system based on software. For example, where 1000 Chinese characters each composed of 24 dotsxc3x9724 dots are displayed in the monochromatic mode, the entire screen can be renewed within about 0.5 to 1 second. In color processing, however, this system faces a problem of degraded performance. Further, the above performance of this prior art system is not enough to comply with performance for renewal of the entire screen within about 0.1 second as requested by a field which takes significant account of the man-machine interface.
An object of this invention is to provide a graphic processing system capable of realizing high speed development of fonts in order to speed up bit map character display.
To accomplish the above object, the present invention provides a processor for managing a display area and a character font area which are included within an address space, and the processor calculates, from coded information indicative of a character transferred through a data bus of a system, an address at which a character font pattern of the corresponding character has been stored and transfers that character font pattern to a predetermined position on the display area.
In the present invention, xe2x80x9ccharacterxe2x80x9d is the concept representative of the fundamental unit of graphic information such as xe2x80x9cEnglish lettersxe2x80x9d, xe2x80x9cnumeralsxe2x80x9d, xe2x80x9cChinese lettersxe2x80x9d, xe2x80x9ckana lettersxe2x80x9d, xe2x80x9csymbolsxe2x80x9d and xe2x80x9cfundamental graphicsxe2x80x9d.